1. Field of the Invention
The invention pertains to a process for operating a strip-casting machine for the production of a metal strip, with two casting rolls set up next to each other to form a casting gap and with lateral sealing elements, which comprise sealing plates on each side of and in close proximity to the casting rolls, where the pressure which the sealing plate applies to the casting rolls and/or the frictional conditions between these components are measured, and where the sealing plates are positioned with respect to the end surfaces of the casting rolls in such a way that the nominal position of the sealing plates with respect to the end surfaces of the casting rolls can be maintained with a very high degree of precision, even at the high temperatures of the casting operation. The invention also pertains to a strip-casting machine for implementing the method.
2. Description of the Related Art
In a strip-casting machine of the type in question according to EP-A 0,714,716, the device for sealing the sides of the casting rolls consists of refractory sealing plates, which are pressed against the end surfaces of the two casting rolls on each side to prevent the steel melt which has been poured in between the casting rolls from escaping toward the sides. Thus a metal bath is formed instead, as in a conventional mold. As pressure is exerted on these sealing plates, they are subjected to frictional wear as a result of the rotation of the casting rolls, this wear being accompanied by large thermal load caused by the molten metal. One of the main problems in a casting machine of this type is therefore to ensure that the lateral sealing elements offer a reliable seal during the entire duration of the casting operation.
In the case of casting rolls with small diameters in the range of approximately 500-800 mm, the seals to be provided for the narrow sides are proportionately smaller. Because of the small volume of the metal bath, however, the surface of the molten bath is unsteady. In the case of the large casting rolls with diameters of, for example, approximately 1,500 mm, the surface of the molten bath is calmer because of its larger volume. Although this is advantageous, larger and more complicated lateral sealing elements become necessary. As a result of manufacturing and installation tolerances, irregular wear, and differences in the degrees to which casting rolls are heated as a result of deposits, it is possible that the sealing edges or sealing surfaces of the rolls are not precisely aligned with each other.
In EP-A 0,692,330, the contact conditions between the sealing walls and the casting rolls are detected by measuring the applied pressure and the frictional conditions, and after these values have been compared with the nominal values, at least one of the casting parameters is adjusted as required. So that such adjustment can be made, each of the sealing walls is held by an arrangement consisting of a main carrier, which can shift in the axial direction of the rolls, and a carrier which is guided horizontally on the main carrier. With this arrangement and with this system for controlling the sealing walls, however, optimal conditions for a long-lasting, satisfactory seal between these sealing walls and the casting rolls cannot be created, especially when work is being conducted with casting rolls with diameters of 1 meter or more.
There is also another document, namely, Patent Abstracts of Japan, Vol. 016, No. 576 (M-13 45), Dec. 16, 1992 and JP 4[1992]-224,052 A, which deals with the measurement of the friction between the end surfaces of the casting rolls of a strip-casting machine and with the appropriate adjustment of the applied pressure as a function of those measurements. To obtain the desired seal between the sealing plates and the end surfaces of the casting rolls, adjustable piston-cylinder units with a pressure control system for the pistons and with a distance sensor for the positioning of the pressure plates are provided. The seal of the end surfaces of the casting rolls by means of the sealing plates is no longer guaranteed by the control of the applied pressure, however, when the end surfaces of the casting rolls are no longer aligned with each other.
Proceeding from these known solutions, the present invention is based on the task of creating a method for operating a strip-casting machine of the general type indicated above, so that, by means of such a method, leak-proof conditions can be ensured at the lateral sealing elements throughout the entire duration of the casting operation even when casting rolls of the optimum diameter are used.
The task is accomplished according to the invention in that the positions of the sealing plates are measured in the direction of the casting roll axis, and in that at least one of the casting rolls can be adjusted, especially in the axial direction, so that the end surfaces of the casting rolls can be aligned with each other on the same plane as accurately as possible.
For a strip-casting machine, the task according to the invention is accomplished in that distance sensors are provided to measure the position of the end surfaces of the casting rolls in the axial direction of the rolls, and in that these distance sensors are in working connection with a device for axially displacing the casting rolls and for aligning the end surfaces of the casting rolls to be sealed with respect to each other.
With this strip-casting machine according to the invention, optimal lateral sealing of the casting rolls is achieved, which sealing function remains intact throughout the entire casting time even in the case of large casting rolls with diameters of more than 1 meter.